Making new items in an array fade in
Please check the BUILD modifier (you can also apply it to lines).
BUILD modified let you animate the generation of a line and on the line/path you can control easily the radius/thickness.

Make 2 curves: one path (the line), one circle or square
one the line apply a GEOMETRY &gt; BEVEL &gt; OBJECT &gt; choose the circle or the square
Edit the size of the path with ALT+S (you can &quot;inflate&quot; a node of the path)
apply the BUILD modifier to the line.
animate and have fun